The present disclosure relates to an emission control device for an internal combustion engine.
Japanese Laid-Open Patent Publication No. 2009-36183 describes an emission control device for an internal combustion engine. The emission control device includes a particulate matter (hereinafter referred to as PM) filter provided in an exhaust passage of the internal combustion engine. The PM filter traps PM contained in exhaust gas. PM includes a substance such as soot generated when fuel is burned in the engine main body of the internal combustion engine and ash generated when lubricating oil is burned. In the emission control device described in the above document, the amount of PM contained in exhaust gas emitted from the engine main body to the exhaust passage is calculated in accordance with the operation condition of the internal combustion engine. A PM accumulation amount, which is the total amount of PM trapped by the PM filter, is calculated by cumulating the calculated PM amount at predetermined intervals. In accordance with the calculated PM accumulation amount, the emission control device executes filter regeneration control for burning and removing PM trapped by the PM filter.
In some cases, when the PM filter is inadvertently left uninstalled during maintenance of the internal combustion engine or when an abnormality occurs in the PM filter due to some reasons, the emission control device hardly traps PM using a PM filter. In this case, the PM accumulation amount calculated by the emission control device no longer indicates the state of the actual emission control device in which PM has hardly been trapped.